The relationship between the reference, AGNDxx and
output voltage is shown in table V.
Table V – Relationship between Reference, AGNDxx and Output
BIPOLAR OPERATION
(AGNDxx = 0 V)
AGNDxx = 0 V
REFxx
–REFxx
(4095/4096)(REFxx)
(REFxx/4096)
((D/4096)–1)(REFxx)
POSITIVE
UNIPOLAR OPERATION
(AGND = REFxx/2)
AGNDxx = REFxx/2
REFxx/2
0V
(8191/8192)(REFxx)
(REFxx/8192)
(D/8192)(REFxx)
PARAMETER
Bipolar Zero Level or Unipolar Mid-Scale
(Code = 1000000000000)
Differential Reference Voltage (VDR)
CUSTOM OPERATION
AGNDxx
REF – AGNDxx
AGNDxx – VDR
AGNDxx + (4095/4096)(VDR)
(VDR/4096)
AGNDxx + ((D/4096)–1)(VDR)
Negative Full-Scale Output (Code = All 0s)
Positive Full-Scale Output (Code = All 1s)
LSB Weight
V
OUT
xx as a Function of Digital Code
(D, 0 to 8191)
Figure 2 – Typical Interface Circuit (shown for unipolar operation)
CMOS/TTL Control Source
Notes
R = 22
Ω
C1 = 1.0
µF
C2 = 0.1
µF
REF = 0 – V
DD
V
FB = Ferrite Bead
R
Analog Buffer
LDGH
D12
D11
D10
CMOS/TTL Data Source
CLR
LDED
LDEF
A0
A2
LDAB
WR
A1
CS
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0 (LSB)
C1
V
DD
V
DD
V
SS
V
SS
GND
REFxx
R
V
OUT
A
V
OUT
B
V
OUT
C
V
OUT
D
V
OUT
E
V
OUT
F
SPT5400
V
OUT
G
V
OUT
H
R
For Bipolar Operation
+A5 V
C1
-A5 V
AGNDxx
C2
R
AGNDxx
FB
+
–
C2
C2
–
+
+
REF
1 kΩ
1 kΩ
SPT5400
6
5/15/00
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
